/*
 * Copyright (c) 2019 Spotify AB.
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package com.spotify.heroic.aggregation.simple

import com.spotify.heroic.ObjectHasher
import com.spotify.heroic.metric.MetricCollection
import com.spotify.heroic.metric.Point
import java.util.*

data class FilterKThresholdStrategy(
    val filterType: FilterKThresholdType,
    val k: Double
) : FilterStrategy {

    override fun <T> filter(metrics: List<FilterableMetrics<T>>): List<T?> {
        return metrics
            .map { Extreme(it, filterType) }
            .filter { it.value.map { v -> filterType.predicate(v, k)}.orElse(false) }
            .map { it.filterableMetrics.data }
    }

    override fun hashTo(hasher: ObjectHasher) {
        hasher.putObject(javaClass) {
            hasher.putField("filterType", filterType, hasher.enumValue<FilterKThresholdType>())
            hasher.putField("k", k, hasher.doubleValue())
        }
    }

    private data class Extreme<T>(
        val filterableMetrics: FilterableMetrics<T>,
        val value: Optional<Double>
    ) {
        constructor(filterableMetrics: FilterableMetrics<T>, filterType: FilterKThresholdType)
            : this(filterableMetrics, findExtreme(filterType, filterableMetrics.metricSupplier!!.get()))

        companion object {
            fun findExtreme(
                filterType: FilterKThresholdType, metrics: MetricCollection
            ): Optional<Double> {
                val stream = metrics
                    .getDataAs(Point::class.java)
                    .stream()
                    .map { it.value }

                return filterType.findExtreme(stream)
            }
        }
    }
}
